Rapid Enlargement of Squamous Cell Carcinoma Arising From Hidradenitis Suppurativa During Bimekizumab Therapy.

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease that can rarely transform into squamous cell carcinoma (SCC), often with aggressive clinical behavior. Biologic agents, including interleukin-17 (IL-17) inhibitors, are increasingly used for severe HS, but their effects on tumor surveillance remain unclear. We report a man in his 50s with paraplegia and a 20-year history of Hurley stage III HS affecting the buttocks and perineum. Four months after initiating bimekizumab for uncontrolled HS, a chronic ulcerative lesion on the left trochanter rapidly enlarged into a 15 cm exophytic tumor. Biopsy confirmed SCC, and biologic therapy was discontinued. Wide local excision with 2 cm margins and sentinel lymph node biopsy were performed, revealing high-grade invasive SCC with negative margins and no nodal involvement. Reconstruction was achieved using a split-thickness skin graft. This case illustrates the malignant potential of chronic HS, particularly in long-standing Hurley stage III disease, and raises concern for the possible acceleration of tumor growth during biologic therapy. Although large studies have not shown increased cancer risk with interleukin-17 inhibitors, vigilance is required when treating patients with HS with biologics. Rapidly progressive or non-healing lesions should prompt early biopsy to exclude malignancy. To our knowledge, this represents the first reported case of HS-associated SCC arising during bimekizumab treatment, emphasizing the importance of careful monitoring in this population.